The present invention generally refers to retractable needles for use in insertion of a catheter. Additionally, the invention relates to hypodermic syringe needles for medical use. More particularly, the invention relates to hypodermic safety needles which retract into a container when not in use, preventing unintentional contact with the needle.
Prior art injection needles and catheter insertion needles feature hollow needles which extend through a plastic hub. To prevent a user from accidentally pricking himself with the point of a needle, the needle is covered with a removable cover. Such covers frictionally engage the plastic hub, and may be readily removed once the needle is attached to a syringe barrel. After use, the cover may be reattached to the needle assembly, which is then separated from the syringe barrel and discarded. However, there is an unacceptable risk of accidental injury resulting from contact with the point of the needle during the recapping step. This is particularly dangerous as biological fluids contaminating the needle could enter the user""s bloodstream. An improved means of covering a used injection needle is needed.
A wide variety of needles having a means for shielding a syringe needle from accidental contact with a user""s fingers have been developed. For example, U.S. Pat. No. 4,900,311, issued to Stem on Feb. 13, 1990, discloses a hypodermic syringe having a syringe barrel, an injection needle attached to the syringe barrel, and a needle guard of elliptical cross section disposed around the syringe barrel. The needle guard may be moved from a first position which covers the needle to a second position which exposes the needle. When the guard is in the second position, tabs on the interior of the guard engage slots on the syringe barrel, locking the guard into position. When the tabs are released from the slots by squeezing the elliptical guard along its longitudinal axis, a spring causes the guard to move into the first position, hiding the needle. The entire syringe assembly is then discarded.
This device, while useful, does have certain drawbacks. The syringe barrel used with this assembly has a highly specialized structure; a generic syringe barrel cannot readily be substituted. Also, the syringe barrel cannot readily be sterilized and reused. No provision for separation of the needle from the syringe barrel without removing the syringe needle from the protective needle guard is provided. Finally, there is the risk of accidentally squeezing the elliptical needle guard, causing the spring to move the needle guard into a position which conceals the needle prior to use of the needle.
U.S. Pat. No. 4,664,654, issued to Strauss on May 12, 1987, discloses a two piece needle shield comprising a sliding member and a stationary member. A latch holds the sliding member in position. When the latch is released, a spring causes the sliding member to retract inside the stationary member, exposing the needle. However, this device causes the user to place his hand in proximity to the needle at the time it is exposed, increasing the likelihood of injury from accidental contact with the needle.
U.S. Pat. No. 5,246,428, issued to Falknor on Sep. 21, 1993, discloses a needle safety mechanism comprising a base adapted to be fixed with respect to the needle, and a sheath which is movable between a first position which exposes the needle and a second position which covers the needle. A latch cooperative between the base and the sheath may be used to releasably latch the sheath in the position which covers the needle. A spring biases the sheath into the needle covering position. No mechanism for latching the sheath in a position which exposes the needle is provided, however. This may be an inconvenience for workers who wish to see the precise spot where they are administering an injection.
U.S. Pat. No. 5,279,579, issued to D""Amico on Jan. 18, 1994, discloses a self-capping injection needle assembly which includes a hub slidably positioned within a cylindrical cover adapted to receive a syringe barrel, and a needle mounted on the hub. A spring biases the hub into a position in which the needle is contained within the tubular cover. When the spring is compressed, the hub may slide into a position which exposes the needle. The hub includes a pin which slidably engages a longitudinal groove in the tubular cover. The groove includes a transverse leg adapted to receive the pin. When the pin is positioned in the transverse leg, the hub is releasably locked into a position which exposes the needle. The hub has a threaded female joint which may be screwed onto a syringe barrel having a corresponded threaded male joint. Different size tubular covers may be used for different size syringe barrels.
This device has certain disadvantages. First, in a medical environment time is often a critical factor. A more rapid method of affixing a needle to a syringe barrel than screwing it on is desirable. Also, only syringe barrels with a specific type of joint adapted to mate with the hub are usable with this device. Most commonly used medical syringe barrels have frusto-conical tips which frictionally engage syringe needle hubs having frusto-conical cavities therein; such commonly used barrels cannot be used with the threaded connections envisioned by D""Amico. D""Amico requires that a hub having a specific diameter must be used with a tubular cover having an inner diameter which is substantially equal to the hub diameter. Most commonly available syringe needle hubs have a single standard size, and cannot be used with a range of tubular cover sizes. Therefore, D""Amico""s invention necessitates creation of a range of expensive and specialized syringe needles having a range of hub sizes. Also, since the diameter of D""Amico""s hub is very nearly equal to the interior diameter of the tubular cover, it is difficult to insert a hub having a protruding pin into the cover. An easy method of assembling such a device is desirable.
U.S. Pat. No. 5,219,338, issued to Haworth on Jun. 15, 1993, and U.S. Pat. No. 5,695,474, issued to Daugherty on Dec. 9, 1997, disclose syringe assemblies in which one end of a retractable sheath is secured to a syringe barrel. The sheaths have circumferential accordion-like pleats which may be folded or unfolded. When the pleats are unfolded, the sheath is in an extended configuration, and covers a hypodermic needle secured to the syringe barrel. When the pleats are folded, the sheath is contracted so as to expose the needle. However, existing syringe barrels either cannot be used with this system, or they must be modified by securing a sheath to the exterior of the barrel before use with this system. Additionally, a wide variety of sheath sizes (one for each size syringe barrel) must be maintained in stock for such a retrofitting operation to be feasible.
U.S. Pat. No. 5,746,727, issued to Graves et al, discloses a safety needle assembly featuring a needle mounted to a hub having a radially projecting compressible knob, and a sheath having a longitudinal slot through which the knob projects. The hub is slidably mounted within the sheath. The slot extends from a first, which grips the knob so as to hold the hub in a position which exposes the needle, to a second locking position, which grips the knob so as to hold the hub in a position which conceals the needle within the sheath. Between the two locking positions, the slot is narrower than the diameter of the compressible knob. Thus, the device requires the application of significant force to move the knob along the slot between the locking positions, making the device awkward to use in situations where the needle must be manipulated rapidly, or handled with one hand.
Dufresne, in U.S. Pat. No. 5,817,065 and U.S. Pat. No. 5,607,402, discloses a safety needle holder having a double-ended needle mounted in a tubular housing. The needle passes through a hub having a pair of knobs which project radially from opposite sides of the hub. The knobs are each engaged by one of two longitudinal slots in the housing, where the longitudinal slots are on opposite sides of the housing. The slots are each of complicated structure, having three locking positions, each with a different shape, and a variety of different widths at different points along their length. The result is a complicated structure which is difficult to manufacture. It would be advantageous to have a housing structure having a slot of reduced complexity which is easier to manufacture.
There is a long-felt need in the art for a safety needle assembly which may be used for drawing blood, giving injections, or insertion of catheters, where the needle assembly has a retractable needle which may be easily assembled, and which may be used with commonly available syringe barrels having frusto-conical tips which frictionally engage a syringe needle assembly. The required safety needle assembly must also avoid the other disadvantages of known prior art devices. It is an object of this invention to provide such safety needle assemblies.
In a first embodiment, the invention is a retractable needle for use with a catheter. The needle features a cylindrical hub having an anterior end and a posterior end, with a hollow needle extending through the hub and projecting from the anterior end of the hub. The hub has a flash chamber connected thereto where the interior of the needle is in fluid communication with the interior of the flash chamber. The hub is slidably positioned in a tubular housing having a tubular wall with a longitudinal slot therein. A stem connected with the hub passes through the slot, and has a thumbrest rigidly fixed thereto, where the thumbrest is on the exterior of the housing and may be used to manually move the knob from a first locking position, where the needle is retracted within the housing, to a second locking position where the needle is exposed. A catheter is mounted on the needle when the needle assembly is exposed.
In a second embodiment, the invention is a retractable needle for use with a syringe. The needle features a cylindrical hub having an anterior end and a posterior end, with a hollow needle extending through the hub and projecting from the anterior end of the hub. The hub has a frusto-conical cavity adapted to frictionally engage the tip of a standard syringe. The hub is slidably positioned in a tubular housing having a tubular wall with a longitudinal slot therein. A stem connected with the hub passes through the slot, and has a thumbrest rigidly fixed thereto, where the thumbrest is on the exterior of the housing and may be used to manually move the knob from a first locking position, where the needle is retracted within the housing, to a second locking position where the needle is exposed.
In a third embodiment, the invention is a retractable needle for use in drawing blood. The needle features a cylindrical hub, with a hollow, double-ended needle extending therethrough. The hub is slidably positioned in a tubular housing having a tubular wall with a longitudinal slot therein. A stem connected with the hub passes through the slot, and has a thumbrest rigidly fixed thereto, where the thumbrest is on the exterior of the housing and may be used to manually move the knob from a first locking position, where the needle is retracted within the housing, to a second locking position where the needle is exposed.
In a fourth embodiment, the retractable needle of the invention features a adjustable-length tube having a first end and a second end. The adjustable-length tube has a length which may be reversibly altered from a first contracted length to a second extended length. A syringe barrel having a frustoconical tip may be secured to the first end of the adjustable-length tube, and a cylindrical hub having a hollow hypodermic needle attached thereto may be secured to the second end of the adjustable-length tube. The interior of the syringe barrel is in fluid contact with the interior of the a hollow hypodermic needle through the adjustable-length tube. A tubular sheath is disposed around the adjustable-length tube. The tubular sheath has a first end which is rigidly connected with the first end of the adjustable-length tube and a second end having an opening which is sufficiently large to allow the end of the hypodermic needle to pass therethrough. The length of the adjustable-length tube may be altered from the contracted length to the extended length. When the adjustable-length tube is contracted, the hypodermic needle is entirely disposed within the sheath. When the adjustable-length tube is extended, the end of the hypodermic needle is exposed through the opening in the second end of the sheath.